Foundation services
Slab lifting and leveling
A good fix for a sunken driveway or patio. The wrong fix for a house whose foundation is moving.
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Written by HyreFoundation Research Desk Primary-source research and fact checking
The short answer
Slab leveling fills the gap under a sunken concrete slab and raises it back toward level, using a cement slurry (mudjacking) or polyurethane foam. It is not underpinning.
Neither method reaches firm bearing soil or fixes why the slab sank. It works well for driveways, patios and garage floors, and poorly for anything carrying the house’s weight through a footing.
Key takeaways
Neither method reaches firm bearing soil or fixes the cause.
driveways, walkways, patios, garage floors, pool decks and basement floor slabs. Wrong for anything carrying structural load.
It adds almost no load to soil that already failed. Slurry adds a lot.
A trade guideline advises leaving it in most cases.
Neither has an ICC-ES acceptance criteria, and the field research is about roads.
When is slab leveling the right fix?
A driveway, walkway or patio section has sunk.
A garage or basement floor slab has pulled down away from the wall.
Fix this one soon. It sends water straight to the foundation. See drainage and grading.
A pool deck or set of steps has settled unevenly.
Erosion, a washed-out utility trench or loose backfill has left a gap under a slab.
A slab has sunk, but an engineer has confirmed the footings and frame are sound.
How does slab leveling work, step by step?
A downspout or leaking line washing soil out, a trench that settled, loose backfill or shrinking clay. If the cause is still active, the slab sinks again and the fill goes with it.
A downspout emptying beside a driveway will undermine it again. The fix is usually cheap, and it decides whether the lift lasts.
A pattern of holes through the slab, sized to the material.
Material is pumped in while the slab is watched with a level or laser. It rises in small steps. Lifting one area faster than the concrete can flex will crack it.
The holes are filled. On a visible surface the patches will show, even when color-matched.
Under a lifted structural slab in expansive clay, a trade guideline says the void should generally remain, so swelling soil has room. An add-on offer to foam it after a pier job may be selling you heave.
Mudjacking or polyurethane foam: which is better?
Both do the same job. They differ in one way that matters, and marketing covers the rest.
| Question | Mudjacking vs. foam |
|---|---|
| What is injected | Mudjacking: a sand-cement or limestone slurry. Foam: a two-part polyurethane resin that expands and cures as closed-cell foam. |
| Weight added | The real difference. Slurry is heavy and cured foam is very light. The slab sank because the soil was weak, so adding weight to that soil works against you. Density figures circulate, but we could not trace them to a manufacturer data sheet. |
| Hole size | Slurry needs larger holes. Foam needs much smaller ones. This matters mostly on a visible finished surface. |
| Cure and use | Foam cures fast, so traffic returns sooner. Slurry takes longer. Exact cure times in marketing are manufacturer claims we did not verify. |
| Water | Cured closed-cell foam does not wash out. Slurry can erode if water keeps moving under the slab, which matters if the cause was erosion and is still active. |
| What neither does | Reach bearing soil, stop future settlement, fix drainage or carry structural load. Both treat a symptom, which is fine when everyone says so. |
To match the method to the problem, try our repair method selector or read repair methods compared.
What moves the price
Slab leveling is usually priced by the amount of material and the area lifted. That makes quotes easier to compare than most foundation work. See what drives foundation costs.
| Factor | Why it changes the number |
|---|---|
| Material | Slurry and foam are priced very differently, and the foam premium is real. Whether it is worth it depends on whether added weight matters at that spot. |
| Size of the void | The unknown, and why quotes carry assumptions. Long-term erosion can leave a void far larger than the visible drop suggests. |
| Area and thickness | Square footage and the number of holes needed. |
| Height of lift | How far it has to rise, and whether the slab can take it without cracking. |
| Access | Whether the rig can reach the area, and what sits on the slab now. |
| Fixing the cause | Drainage, a plumbing repair or compacting backfill. Usually a separate line, and usually what decides whether you pay once. |
HyreFoundation publishes no national average price for this work. Depth to bearing, soil, access and method vary enough between two houses on the same street that a single figure would mislead.
Is the slab part of the house’s foundation?
If so, slab leveling is the wrong tool. It suits a slab that sank on its own. If floors slope through the house, doors stick and walls crack, the building is settling. That needs an assessment and possibly underpinning. Foam under a settling foundation raises the floor and leaves the cause alone.
What to ask before you sign
Why did this sink, and what stops it happening again?
Is the house involved, or is this slab sinking on its own?
How much material do you expect, and what if the void is bigger?
How much lift are you aiming for, and what is the risk of cracking?
Where will the holes go, and how visible will they be?
Can I see the manufacturer’s technical data sheet for the material?
What does it cover, and does it exclude further soil settlement?
Should any part of this void stay unfilled, and why?
The full checklist is on choosing a foundation contractor.
What to have ready
The sunken area, ideally with a straightedge showing the drop.
How far it has dropped, and when you first noticed.
Whether it is still moving, and whether it changes by season.
Downspouts, irrigation, a utility trench, a big tree or a known plumbing repair.
Whether water now runs toward the house because of the drop.
Where this goes wrong
The most common way to pay twice. If water still undermines the slab, the material follows it down.
Neither method reaches bearing soil. A settling foundation lifted with foam looks better and is unchanged.
In expansive clay, after underpinning and lifting, the gap under a slab is often left on purpose. Filling it can cause heave.
Concrete tolerates only so much uneven movement. An aggressive lift cracks the slab you are trying to save.
Hole patches show. On stamped or decorative concrete, ask to see photos of past jobs first.
Expansion ratios, cure times and density claims circulate widely. We could not trace them to manufacturer data sheets. Ask the contractor for the data sheet.
Get connected
Tell us about the work
Three short steps: the job, your home, and how to reach you. Nothing goes to a foundation company unless you agree.
A straight answer first. Matching is still being built, so this is not an instant quote. If a wall is moving or a door frame has racked out of square this week, call a structural engineer first.
Find a Foundation Professional
Tell us what you are seeing and where you are. We will follow up about connecting you with foundation professionals serving your area.
Questions
Is polyurethane foam better than mudjacking?
How long does slab leveling last?
Can slab leveling fix sloping floors inside my house?
Is there research showing foam injection works?
Will slab leveling crack my concrete?
Does it matter if my driveway slopes toward the house?
Written and audited by
HyreFoundation Research Desk
Primary-source research and fact checking
We read the model building code, the federal soil and moisture guidance and the insurer position ourselves, and we publish each figure with the document it came from and the date we retrieved it.
Where a number cannot be traced to a primary source, we say so instead of printing it. HyreFoundation does not inspect, engineer or repair foundations. Authorship is organizational: this desk, not a named persona.
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How this desk works
- Primary sources only. Code statements come from the International Residential Code, Chapter 4, as the model code. Soil statements come from USDA and USGS. Insurance statements come from the policy language and the Insurance Information Institute. We open the source rather than cite a blog that cites it.
- The code is a model, and adoption is local. Your jurisdiction adopts an edition and amends it, and foundation chapters are amended more than most because frost depth and soil are local facts. Every code figure says so.
- We hold no job data. We have no dataset of bids, pier counts or invoices, so no page claims an average from one. Calculators show the arithmetic and the inputs they assumed, and label the result as an estimate.
- We do not diagnose your house. A crack guide can tell you which pattern to measure and when to call a structural engineer. It cannot tell you whether your foundation is failing. An engineer on site does that work.
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Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
Information on this page is general and varies with soil, climate, foundation type, building code, insurance policy and circumstance.
It is not engineering, insurance or legal advice, and no page can tell you whether your house has a structural problem: that needs a licensed professional on site.
HyreFoundation is an independent foundation resource, not a repair contractor or an engineering firm, and does not perform, supervise or warrant foundation work.